Axial compressor

Abstract

An axial compressor comprises a stator component and a rotor component, which cooperate to perform work on a fluid flow in a primary flow-passage defined by the stator and rotor components, the stator component and the rotor component further defining a secondary flow-passage which interconnects a higher pressure region and a lower pressure region of the primary flow-passage, the rotor component being provided with at least one secondary rotor element which, in normal operation of the machine, pumps a bypass flow of fluid through the secondary flow passage from the lower pressure region to the higher pressure region.

1. An axial compressor comprising a stator component and a rotor component which cooperate to perform work on a fluid flow in a primary flow-passage defined by the stator and rotor components, the stator component and the rotor component further defining a secondary flow-passage which interconnects a higher pressure region and a lower pressure region of the primary flow-passage, the rotor component being provided with at least one secondary rotor element which, in normal operation of the machine, pumps a bypass flow of fluid through the secondary flow passage from the lower pressure region to the higher pressure region. 
     
     
       2. The axial compressor according to  claim 1  in which the rotor component and the stator component provide a primary flow stage comprising an annular row of rotatable blades and an annular row of stationary blades in axial flow series with the rotatable blades for introducing a static pressure differential in a flow passage constituting the primary flow-passage, the rotatable blade row forming part of a rotatable assembly which extends axially through the annular stationary blade row and which is separated from the stationary blades by a running clearance constituting the secondary flow-passage, the or each secondary rotor element being provided on the rotatable assembly for driving a bypass flow generally axially through the running clearance, towards the nominal high pressure side of the stationary blade row, thereby to limit pressure-driven leakage underneath the stationary blades. 
     
     
       3. The axial compressor according to  claim 2 , wherein the running clearance is provided by a recess between spaced apart hub sections of the rotor assembly that form part of an axially-segmented inner wall of the flow passage, the recess extending axially underneath the stationary blades from the nominal low pressure side of the stationary blade row to the nominal high pressure side of the stationary blade row. 
     
     
       4. The axial compressor according to  claim 3 , wherein the secondary rotor elements are located in the recess for drawing said bypass flow into the recess on the nominal low pressure side of the stationary blade row and driving the bypass flow out of the recess on the nominal high pressure side of the stationary blade row. 
     
     
       5. The axial compressor according to  claim 3 , wherein the stationary blades are radially shielded from the bypass flow in the recess by a shroud at or near the inner end of the stationary blades, the shroud and recess forming a shroud cavity having a circumferential intake slot between the shroud and the first hub section, and a circumferential discharge slot between the shroud and the second hub section. 
     
     
       6. The axial compressor according to  claim 5 , wherein the shroud supports one or more stator elements inside the shroud cavity in axial flow series with the secondary rotor elements inside the shroud cavity. 
     
     
       7. The axial flow turbo machine according to  claim 6 , wherein the shroud supports one or more stator elements between the secondary rotor elements and the intake slot for turning the bypass flow onto the rotor elements. 
     
     
       8. The axial compressor according to  claim 6 , wherein the shroud supports one or more stator elements between the secondary rotor elements and the discharge slot for removing swirl from the bypass flow. 
     
     
       9. The axial compressor according to  claim 5 , wherein the shroud forms an annular intake slot with the first hub section for receiving an axial intake flow. 
     
     
       10. The axial compressor according to  claim 9 , wherein the annular width of the intake slot corresponds to the nominal thickness of a primary flow boundary layer on the first hub section. 
     
     
       11. The axial compressor according to  claim 9 , wherein the shroud and/or rotor assembly are configured for co-operatively guiding bypass flow through the intake slot and down into the shroud cavity. 
     
     
       12. The axial compressor according to  claim 11 , wherein the shroud is banked near the intake slot for guiding bypass flow entering the intake slot down into the shroud cavity. 
     
     
       13. The axial compressor according to  claim 5 , wherein the shroud and the rotor assembly are configured for co-operatively vectoring bypass flow through the discharge slot thereby to increase the axial momentum of by pass flow exiting the discharge slot. 
     
     
       14. The axial compressor according to  claim 13 , wherein the shroud is banked near the discharge slot for turning the bypass flow axially through the discharge slot thereby to increase the axial momentum of the bypass flow exiting the discharge slot. 
     
     
       15. The axial compressor according to  claim 14 , wherein the shroud forms an annular discharge slot with the second hub section for discharging a substantially axial bypass flow. 
     
     
       16. The axial compressor according to  claim 15 , wherein the annular width of the discharge slot corresponds to the nominal thickness of the primary flow boundary layer on the second hub section for increasing the axial momentum of the boundary layer.